A. Field
This invention relates generally to the field of wireless telephony and more particularly to methods of determining the geographic location of a mobile telephone and providing such location information to a user, computer application, or other source requesting the information.
B. Related Art
The art of wireless telephony has developed various methods for determination of the location of a wireless telephone. Some methods analyze the signals exchanged between the telephone and base station antennas in the wireless network. Other methods make use of Global Positioning System (GPS) chips which are included in the wireless telephone and the transmission of GPS data from the telephone to a network node. In the art, such techniques result in relatively high precision determination of the location of the wireless telephone, often to within an accuracy of a hundred feet or even less.
High precision location determination capabilities, such as described above, are used for a variety of purposes, including directing a response to an emergency 911 (E-911) call placed by the wireless phone, and providing location-based services to the user of the wireless phone. Examples of the determination and use of a location of a wireless telephone are set forth in the following patent documents, all of which are assigned to the assignee of this invention: U.S. Pat. Nos. 7,142,874; 7,130,641; 7,092,722; 7,031,714; 6,956,931 and 6,816,735. Other prior art of interest includes Bergkvist, et al., U.S. Pat. No. 6,091,958; Olrick et al., U.S. Patent application publication 2003/0125042; Published PCT application WO 2004/105295, published European Patent Application EP 1,248,484 and Nandini Krishnamurthy et al., Using SMS to deliver location-based services, 2002 IEEE International Conference on Personal Wireless Communications, Dec. 15-17 2002, pp. 177-181.
The use of location information in the wireless telephone art for these and other purposes has been growing at an extremely rapid rate. The present inventors have realized that high precision wireless telephone location systems are difficult and expensive to scale to the levels needed to satisfy the demand for location determination. This is due to several factors, including the fact that many wireless telephones, particularly older ones, do not have GPS chips in them and thus more time consuming and expensive methods must be used, the ever growing number of wireless telephones in use, and the ever increasing number of uses and applications for wireless telephone location.
One example of the use of high precision location information is so-called “idle mode location query” (IMQ), which refers to the scenario where one user (user A) wants to pinpoint the location of another user (user B) whose mobile handset is in idle mode. Idle mode means the mobile handset is powered on, but not engaged in any active voice or data session. In current practice, User A can initiate a location request through a mobile service provider's web site or a specially designed enterprise application server which is connected to the service provider's network via a Virtual Private Network. When the service provider's location platform receives the location request, it will first wake up the GPS chipset of the target handset (user B's handset) and then set up a location session with the handset. After the position of the target handset is calculated (through GPS or network based location technology such as Advanced Forward Link Trilateration (AFLT) (a location method based on signal measurements), the location platform returns the results back to User A.
IMQ capability is a significant business driver for wireless service providers. It has been widely used by both commercial and enterprise users. For example, a mother may want to find out whether her son has arrived at school and uses IMQ to determine whether the son is at the location of the school. As another example, a taxi company manager wants to know the location of a cab and uses the above method to locate the cell phone used by the cab driver. The current IMQ solution described above, however, has the following shortcomings:                The target handset (the handset to be located) has to have an embedded GPS chip if GPS technique is to be used.        The target handset must be IMQ capable (i.e. the handset GPS chip must be able to be woken up by a network message).        The IMQ location request, just like the handset initiated location request, requires a location session to be established between the handset and the location platform. The session usually lasts 20 seconds. Such a location procedure consumes a lot of network resources at the location platform, Mobile Switching Centers (MSCs) and air interface resources. With the explosive increase in the demand for IMQ location services, the capacity issue will escalate in severity in the foreseeable future.        
Preferred embodiments of this invention make use of Short Message Service (SMS) messaging. SMS is a known means by which short (up to 160 characters) alphanumeric messages can be sent to and from digital cell phones, pagers and other hand=held wireless devices. SMS is defined in the international standards document IS-41C. An outline of SMS is described in Gallagher et al., Mobile Telecommunications Networking with IS-41, chapter 13, McGraw-Hill Series on Telecommunications (1997). SMS is basically a store and forward method for delivering SMS messages to mobile terminals. Generally, when a network entity (which could also be a mobile device) sends an SMS message, the message gets sent as an “SMPP” message to an SMS router, which delivers the message as an SMPP message to an SMS Center (SMSC) based on the destination party's number indicated in the message. In particular, the SMS router in queries a network entity to find out which SMSC serves the destination and then sends the message to the serving SMSC. The SMSC will then query a home location register (HLR) to find out which mobile switching center (MSC) currently serves the terminating mobile station, and will send the SMS message to that switch in an “SMDPP” message. The MSC then pages the mobile station by transmitting a general page message, and the MSC receives a general page message response from the mobile station, indicating the mobile station's serving cell/sector. The MSC then delivers the SMS message to the mobile station via the base transceiver station that operates the indicated serving cell/sector. Further, the MSC sends an smdpp_rr (an SMDPP return result or acknowledgement) message to the SMSC to acknowledge message delivery.
This invention meets a need in the art for a method for locating a wireless telephone but in a more scalable, cost effective and efficient manner than the high precision methods using GPS or triangulation methods. The methods of this invention may not have the high precision of GPS or triangulation algorithms currently used in E-911 services, but the lower precision location is still more than adequate for many other applications.
One aspect of this invention is directed to an SMS-based relatively low precision IMQ solution which is able to resolve all the above mentioned issues by offloading some of the location requests (those where lower precision is acceptable) from the high precision location platform to SMS infrastructure of a wireless service provider network.